A toroidal continuously variable transmission (toroidal CVT) includes power rollers disposed in a cavity formed by an input disc and an output disc. The power rollers are driven by an actuator and displaced such that the power rollers are tilted within the cavity. A transmission ratio (transmission gear ratio) of the toroidal CVT is continuously changed by changing tilt motion angles of the power rollers.
In a case where the transmission ratio of the toroidal CVT is controlled, target roller positions are derived so that a deviation between an actual transmission ratio and a target transmission ratio can be cancelled, and an operation command value of an actuator is derived so that deviations between actual roller positions and the target roller positions can be cancelled. To simplify a hardware for controlling the transmission ratio, a method of estimating the actual roller positions based on as inputs tilt motion angles of the power rollers and the operation command value of the actuator has been conventionally proposed (e.g., see Patent Literature 1).